Dual-faced knits, wovens and laminates are known in the textile art. Since these fabrics are constructed exclusively with yarns that have rather high density, and since they have to be relatively densely woven or knit to be durable, the resulting fabrics exhibit low drying speeds and have relatively low bulk and absorbency per unit weight. Such traditional fabric structures are only capable of absorbing a few times their weight in water, and have relatively long drying times. In apparel applications where perspiration occurs (e.g., sportswear and underwear), lightweight fabrics that feel dry (i.e., have a "water transport" face against the skin that does not absorb water itself) and absorb and evaporate perspiration quickly are very desirable. Experience in the art has indicated to the applicants that an absorbent fabric capable of holding at least 200 gms of water per square meter, that has a uniform nonabsorbent face of textile fibers (no gaps wider than 3 mm) weighing at least 10 gms/sq m, and that can dry quickly in open air, would act as an effective comfort fabric. However, the lightest constructions of present day dry-feeling knit or woven dual-faced fabrics of this type of construction (e.g., double knits) weigh at least 150-300 gms per sq. m, tend to be uncomfortable because of their sheer weight, and tend to be costly. A durable, absorbent fabric equipped with a "transport" layer that could perform this function at a much lower weight (e.g., a fabric basis weight of 20 to 120 gms per sq. m), and that could hold water at least 5 times its weight, with a bulk of at least 10 cc/gm (for quick-drying), would be very desirable.
Low-density absorbent and nonabsorbent stitchbonded nonwovens are also known. For instance, U.S. Pat. No. 4,773,238 (Zafiroglu) and copending U.S. patent application Ser. No. 07/584,161 filed Sep. 18, 1990, both describe fabrics stitched with elastic or bulkable yarns. These fabrics improve in bulk and absorbency after stitchbonding when the product is allowed to contract, "gather" and "bulk-up". Even higher bulk and absorbency values are achieved in the fabrics disclosed by U.S. Pat. 4,876,128 (Zafiroglu), wherein the degree of bulking is controlled by regulating post-stitching shrinkage. Absorbencies that go as high as 15 times the weight of the fabric are reported. However, in all of the above-identified stitchbonded fabric references, the fabric is constructed with only one layer of a nonwoven substrate, and no attempt is made to construct a dual-layered fabric. In this regard, Examples 3-1 and 3-2 of copending U.S. Ser. No. 07/584,161 are believed to come the closest. These examples disclose a pre-needled substrate containing 55 wt. % woodpulp. This construction results in a fabric that is heavy, relatively dense and slow-drying (bulk 3.3-5.8 cc/gm and absorbency 2.3-3.9 times the weight of the fabric).
Additionally, in the above-identified references, no effort is made to construct a nonabsorbent "transport" layer wherein yarn segments are placed over the absorbent nonwoven substrate. In order to build a 10 gm/sq. m nonabsorbent "transport" layer formed with yarn segments within the limits of U.S. Pat. No. 4,773,238, U.S. Pat. No. 4,876,128 or copending U.S. Ser. No. 07/584,161, with the surface yarn segments leaving stitching gaps no wider than 3 mm, and with at least one bulkable yarn stitched in, the total yarn consumption as stitched would have to be at least 15 gm/sq. m. The weight of yarn per unit area will then grow substantially higher as the fabric is relaxed and gathered.
In U.S. Pat. No. 4,773,238, the yarn content does not exceed 20% of the weight of the fabric. In addition, the fabric is gathered to less than 40% of its original stitched dimensions. With 15 gms/sq. m of yarn, the total fabric weight would be at least 15.times.5.times.2.5=187 gm/sq. m which would come close to exceeding the preferred weight limits of the reference, even at the maximum yarn level of 20 wt. %.
U.S. Pat. No. 4,876,128 does disclose bulkable yarns having up to a 20 wt. % yarn content and requires lower levels of shrinkage (a minimum of 10%). The same calculation performed above for U.S. Pat. No. 4,773,238, repeated for the extremes of U.S. Pat. No. 4,876,128, would require a minimum weight of 15.times.1.1.times.5=83 gm/sq. m. Although this is a suitable basis weight for purposes of the applicants' present invention, all examples in U.S. Pat. No. 4,876,128 which contain a relatively large amount of yarn (such as samples D, E, and F--10.7 to 11.7 wt. % yarn) have bulks lower than their prescribed limits (e.g., 13.0-14.1 cc/gm vs. 16 cc/gm minimum). Thus, the very high fabric bulks required by U.S. Pat. No. 4,876,128 cannot be obtained with high surface density yarn segments unless relatively heavy starting webs, highly-bulked to counteract yarn weight, are used. The webs disclosed in U.S. Pat. No. 4,876,128 start at a fabric weight of 103 gm/sq. m. With a minimum yarn weight of 15 gm/sq. m added, and the fabric shrunk at least 10%, the total minimum weight of the fabric would exceed 129 gms/sq. m (i.e., (103+15) 1.1=130 gms/sq. m).
Copending U.S. Ser. No. 07/584,161 recommends yarn percentages under 20 wt. %, but does disclose the use of higher yarn weight percentages. However, in the applicants' experience, in order to construct a comfort fabric, a low-density absorbent substrate (such as a lightly spunlaced staple web containing rayon or cotton or less than 25% woodpulp) must first be selected. The substrate selected must be chosen to be absorbent, have high bulk, low weight, and the stitch pattern would have to be arranged to provide a minimum weight of nonabsorbent yarn of 10 gm/sq. m exposed on one face. The stitch spacings or gaps would have to be no wider than 3 mm, the shrinkage of the fabric would have to be controlled to maximize bulk and avoid fabric densification due to excessive area gathering, and the yarn substrate materials would have to be chosen to allow rapid drying. In this regard, U.S. Ser. No. 07/584,161 does not contain any teaching or examples that approach these conditions. All examples provided in U.S. Ser. No. 07/584,161 are deficient in at least three of the areas the applicants have found necessary to make a comfort fabric. In general these areas of deficiency include:
(1) There is no provision for an absorbent substrate having low-density and quick-drying properties;
(2) When a satisfactory "transport" layer is inadvertently formed with yarn segments, the resulting fabric is overshrunk, overdensified and overweight; and
(3) If the fabric is not overshrunk, the "transport" layer is not properly formed because the yarn gaps or spacings are too large (i.e, more than 3 mm).
Moreover, copending U.S. Ser. No. 07/584,161 and U.S. Pat. No. 4,876,128 utilize textured nylon as the wrapping yarn over "Lycra.RTM.", or as the main yarn. Nylon, and especially textured nylon, tends to absorb over 10 wt. % water and to hold onto water for extended periods of time. (10 wt. %+regain). This causes the fabric to feel relatively wet when it comes in contact with a wearer's skin.
In summary, none of the above-identified references disclose a dual-layered comfort fabric having a separate, nonabsorbent "transport" layer; and if a transport" layer is inadvertently formed, it is not formed by yarn segments unless conditions are chosen at the extremes. Under these extreme conditions, the fabrics formed do not serve their intended prior art purposes. Moreover, as set forth in the Examples which follow (particularly Examples C and D), the fabrics formed serve the purposes of a comfort fabric very poorly.
Clearly, what is needed is a comfort fabric that does not have the deficiencies inherent in the prior art. It is therefore an object of the invention to provide for a lightweight, bulky comfort fabric which has a separate, nonabsorbent "transport" layer formed by stitched yarn segments or by a nonwoven web. Other objects and advantages of the present invention will become apparent to those skilled in the art upon reference to the attached drawings and to the detailed description of the invention which hereinafter follows.